The present invention relates to method of controlling the load in an electric circuit, and more particularly to such a load control method which controls the load by means of detecting the time state of same frequency alternating current sine wave and alternating current square wave.
In certain electric systems, an interruption of power supply may cause a big loss. In order to eliminate this problem from an electric system, an unceasing power system or uninterrupted power supply shall be installed. Further, regular emergency fixtures have self-provided battery power supply. When city power supply fails, the self-provided battery power supply is automatically started to turn on the load. In order to obtain sufficient illumination in a big space, a big number of emergency fixtures shall be used. It is not economic to install a big number of emergency fixtures in a space.
The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a load control method, which controls the load of an electric system object to the condition of provided power supply between city power supply and unceasing power system power supply. It is another object of the present invention to provide a load control method, which imperatively drives the load to work upon a failure of city power supply. According to the present invention, the method of controlling the load in an electric system is achieved by means of detecting the time state of same frequency of alternating current sine wave and alternating current square wave. The method includes the step of picking up a half cycle wave signal, then attenuating the picked up half cycle wave signal and shaping the signal into a pulse wave signal, the step of chopping the picked up half cycle wave signal and shaping the signal into a square wave signal and then delayed the square wave signal, the step of comparing the rising edge of the square wave signal with the descending edge of the pulse signal so as to obtain a time difference, and the step of controlling the load of the electric circuit by means of a first control mode if the voltage level of the time difference thus obtained is at low potential, or by means of a second control mode if the voltage level of the time difference thus obtained is at high potential.